Pickling apparatus



Sept. 19, 1961 SHAY ,3

PICKLING APPARATUS Filed Oct. 30, 1957 2 SheetsSheet 1 ls k 23 m T Q3\JLB3 29 31 X 20 2:5?- 30 X4 INVENTOR Eli Shay United States Patent 6Filed Oct. 30, 1957, Ser. No. 693,369

Claims. (Cl. 13457) This invention relates to apparatus for the cleaningof products of substantial length by passing them in a substantiallycontinuous manner through a pickling tank.

In the treatment and fabrication of many products of extended length,such as ferrous strip and wire products, for example, it is frequentlynecessary that the products be cleaned prior to performing a particularoperation upon them. The cleaning process may be acid or alkaline and isgenerally known as pickling. Speaking by way of illustration, hot rolledsteel strip is ordinarily covered with mill scale of ferrous oxidesresulting from its exposure to air at elevated temperatures. The scalemust be removed prior to cold rolling to avoid inclusions of scale inthe cold rolled strip. The strip is, therefore, passed through a tankcontaining an acid pickling solution. The problems or" handling thestrip at either end of the pickling tank, of welding coils to form acontinuous strip before pickling, and of cutting the strip intomanageable lengths after pickling, may reduce the strip speed in thepickling tank below the usual operating speed or require that the linebe stopped momentarily. Despite such variations in speed and stops, theprocess is substantially a continuous one in which the product movesthrough the tank as an endless member approximating a predeterminedspeed.

It is necessary for eflicient operation to add acid and watercontinuously to the pickling bath to maintain a proper concentration ofacid and iron in the bath for optimum removal of the mill scale from theproduct. Heretofore, acid and water have been added at a predeterminedrate calculated from the average speed and width of strip passingthrough the pickling tank. Hourly or more frequent titrations have beennecessary to check the acid concentration in the tank and to make fineadjustments in the acid and water flow, in accord with the results ofthe titrations. Regular corrections in the rate of acid and water flowhave been necessary, and it has generally been necessary to overcorrectfor the purpose of restoring a proper balance. To provide againstinsuificient pickling, an excess of acid has normally been carriedresulting in a waste of acid and acid attacks on the product afterremoval of the scale. Regardless of the particular product beingpickled, certain problems will usually be present in some degree. Theflow of the pickling agent must be controlled to maintain a sufficientconcentration for complete pickling, while holding attacks on the metalto a minimum. The maintenance of optimum conditions in the pickling tankreduces the amount of waste product which must be disposed of, and ishighly desirable for this reason alone, the disposal of pickling wastebeing a major operating problem.

I provide means for continuously pickling a product comprising apickling tank through which the product is passed, product measuringmeans to continuously measure the rate at which the product passesthrough the tank and control means to introduce a pickling agent intothe tank at a rate proportional to the rate of passage of productthrough the tank. I prefer to provide product speed measuring means andmeans to indicate the product size whereby the product area rate ofpassage through the pickling tank may be determined. I prefer to provideproduct speed measuring means, pickling agent control means inconnection therewith and pickling agent gauge means whereby the rate offlow of the pickling agent may Patented Sept. 19, 1961 ice be determinedfor further adjustment of said flow. I further preferably providecontrol means for a dilutent in operative connection with the picklingagent control means whereby the dilutent may be introduced into thepickling tank proportionally with the pickling agent.

Other details, objects, and advantages of the invention will becomeapparent as the following description of a present preferred embodimentthereof proceeds.

In the accompanying drawings, I have illustrated a present preferredembodiment of my invention in which FIGURE 1 is a diagrammatic viewshowing a portion of a pickling tank with the associated controls beingshown diagrammatically; and

FIGURE 2 is a side View of the exit end of a conventional pickle lineembodying the invention, showing a portion of the pickling tank, thepinch rolls which pull strip through the pickling line and the stripwashing and drying apparatus positioned between the pickling tank andpinch rolls.

in the accompanying drawing, a pickling tank is illustrated which issuitable for acid pickling of hot rolled strip prior to cold rolling.The handling of such strip is generally well-known. A particular type ofinstallation is shown, for example, in United States Patent 2,196,600 toRaymond J. Wean and Donald A. McArthur. A portion of a pickling tank 1is shown diagrammatically. The strip S passes into the pickling tank atirregular speeds because of normal operating conditions. The strip ispulled from the tank between a pair of conventional pinch rolls in acontinuous operation, although the speed varies widely, and the stripmay even be stopped at times. One of the I pinch rolls is illustrated at2 and has a tachometer generator 3 connected to it. The pinch roll iscontinuously in contact with the strip whereby it and the connectedgenerator will rotate at a speed proportional to the strip speed,producing a proportional electric signal. The sig nal is transmitted onwires 4 to a transmitter 5 which will deliver air to a pipe 6 at apressure proportional to the generated voltage. A FoxboroE.M.F./pneumatic transmitter is a satisfactory instrument for thispurpose. A manually set valve 7 supplies a regulated amount of air to apipe 8. The valve supplies air at a reduced pressure which isproportional to the opening of the valve, and is calibrated in inches ofstrip width. Thus, by appropriate setting of valve 7, an air pressure inpipe 8 is maintained which is proportional to the strip width. A Foxboropneumatic airdron type 20 supply regulator is suitable at this point. Amultiplier 9 multiplies the pressures in pipes 6 and 8 and transmits aresultant pressure in pipe 10. Consequently, the pressure in pipe 10will be proportional to the area of strip passing through and leavingthe pickling tank. A Foxboro M/40 black box computer is a satisfactoryinstrument for these purposes. A recorder 11 of conventional designcontinuously records the pressures in pipes 6 and 8 on a chart to make apermanent record, as well as to give visual indication of the pressuresat any moment.

Sulfuric acid used for pickling is maintained in a head tank 12 andfeeds through a supply pipe 13 into the pickling tank at a dischargepoint 14. Pipe 10 leads to a controller 15 which transmits the pressurethrough the pipe 16 to valve 17 in acid supply pipe 13. Valve 17 opensan amount proportional to the air pressure in pipe 16, thereby allowingacid to pass into the pickling tank in an amount proportional to thearea of strip then passing into the pickling tank. A Foxboro stabilfiowide range control valve is suitable for this purpose. A solenoid valve19 is normally maintained in open position but may be operated to closepipe 16, thereby stopping acid flow into the tank. It will be apparentthat small variations in the acid flow may occur due to variations oflevel in head tank 12, inaccuracies in valve and in strument settings,and the like. A magnetic flow meter 20, such as that employed in aFoxboro magnetic flow control meter system, is placed in acid supplypipe 13.

The Flow meter measures the rate of 130W of acid in supply pipe 13 andtransmits a proportional electrical signal through wires 21 to acontroller 15 such as a Poxboro dynalog electronic indicating controllertransmitter with stabilog control mechanisms, Model No. 9653 44-4-8.By-pass valves 18 are provided around valve 17 and flow meter 20 formanual and emergency operation. I

Controller 15 is responsive to the voltage in wires 21. It thenmodulates the pressure in pipe :16 to maintain an accurate flow insupply pipe 13 which is proportional to the pressure in pipe 11. Thisfeedback serves to check the actual acid input continuously and to matchit accurately to the signal indicating the rate of strip passage throughtank 1. Controller 15 also records the actual flow of acid in supplypipe 13 on a chart and transmits in pipe 22 a pressure proportional tothe actual flow of acid in the supply pipe 13. A dial type recorder 23such as a Foxboro integrating recorder maintains a record of the totalamount of acid discharged into tank' l.

A proportioning controller 24 is connected to pipe 22 and delivers acontrolled air pressure in pipe 25 which is proportional to the pressurein pipe 22. The ratio or proportion may be manually set on controller24. A Foxboro recording receiver ratio cont-roller, type M/4O stabilogis suitable for this purpose. Air pressure in pipe 25 opens a pneumaticvalve 26 proportionally, thereby discharging water through pipe 27 intothe pickling tank at discharge point 28. A flow meter 29 connectedacross an orifice 30 records the actual flow of water in pipe 27. Manualby-passes 31 are provided around the valve 26 and orifice 30. The flowmeter develops an air pressure in pipe 32 proportional to the actualflow of water through orifice 30. Pipe 32 connects to a proportioningcontroller .34 such as a Foxboro indicating flow transmitter and servesas a feedback from which controller 24 further adjusts valve 26 tomaintain a correct flow of water in pipe 27. A dial type recorder 33,such as a Foxboro pneumatic receiver integrator, records the totalgallons of water discharged into the pickling tank. Two pens incontroller 24 continuously record the flow of acid and of water intopickling tank 1.

From the foregoing, it will be apparent that the area of strip passingthrough the pickling tank is constantly being determined and that acidis delivered'to the pickling tank in a fixed proportion thereto. Theactual flow of acid is measured, and this information is fed back to thecontroller for further precise adjustment of the acid {flow controlvalve. In like manner, water is supplied to the pickling tank in anamount proportional to the acid flow. Similarly, the actual water flowis measured and fed back to the Water flow controller for furtheradjustment of the Water flow control valve. The acidwater ratio isadjusted manually to suit the particular operating conditions. Once set,this ratio is ordinarily maintained constant for given operatingconditions, and future adjustments are made only infrequently, Theamount of acid supplied may be cut ofi ,or increased through manualcontrol to meet abnormal operations conditions or make corrections inthe acid concentration if necessary. It has been found that the desiredacid concentration is maintained much more closely than is possible withmanual control. The time between titrations of the pickling tanksolution has been increased, thereby reducing the labor required. Overlystrong acid solutions are avoided, thereby making more efiective use ofthe acid and minimizing acid attack on the product. It will be apparentthat use of the invention is not limited to wide thin strip or any otherproduct, that it may be used with products of other types and crossSCfions,

such as wire, for example, and that any desired pickling agent may beemployed.

While I have illustrated and described a present preferred embodiment ofmy invention, it is to be understood :that I do not limit my selfthereto and that the invention may be otherwise variously practicedwithin the scope of the following claims.

I claim:

1. Apparatus for continuously pickling a product comprising a picklingtank through which said product is passed, measuring means to measurethe speed at which the product passes through the tank, and meansresponsive to said measuring means to introduce a pickling agent intothe tank whereby the pickling agent is introduced at a rate proportionalto the measurement of said measuring means.

2. Apparatus for continuously pickling a strip product comprising apickling tank into which said strip product is introduced, means tomeasure the rate of passage of the strip product through the tank, andmeans responsive to said first means to introduce a pickling agent intothe tank at a rate proportional to said rate of passage of stripproduct, whereby the rate of introduction of the pickling agent varieswith the rate of passage of the strip product through the pickling tank.

3. Means for continuously pickling a product of substantial lengthcomprising a pickling tank through which said product is passed,measuring means to continuously measure the area of the product passingthrough the tank per unit of time, and means responsive to saidmeasuring means to introduce a pickling agent into the tank at a rateproportional to the area of product passing through the tank.

4.. Means for continuously pickling a product of substantial lengthcomprising a pickling tank through which the product is passed byconcurrently introducing and removingthe product from the tank, means tomeasure the rate of removal of the product from the tank, and secondmeans responsive to first said means to introduce a pickling agent intothe tank at a rate proportional to the rate of removal of the productfrom the tank, whereby the rate of introduction of pickling agent iscontinuously varied with the rate of removal of the product from thetank.

5. Means for continuously pickling a product of substantial lengthcomprising a pickling tank through which the product is passed, productspeed measuring means adjacent the point of removal of the product fromthe tank, means in operative connection therewith adjustable for thesize of the product being pickled whereby the area of product passingthrough the pickling tank is determined, and means controlled by theproduct speed measuring means and the means in operative connectiontherewith to introduce a pickling agent into the tank at a rateproportional to the rate removal of the product.

6. Means for continuously pickling a strip product of substantial lengthcomprising a pickling tank through which the strip product is passed ata variable speed, strip speed measuring means adjacent the point ofremoval of strip from the tank and indicating the speed of removal ofthe strip, means to indicate the size of the strip, means responsive toboth said means whereby the rate of strip product area passing throughthe pickling tank is determined, and means in operative connectiontherewith to feed a pickling agent to the tank at a rate proportional tothe rate .at which strip product area is passing through the tank.

'7. Means for continuously pickling a product of substantial lengthcomprising a pickling tank into which the product is introduced atvarying speeds, speed measuring means to measure and indicate the speedof passage of product through the tank, indicating means in connectiontherewith and adjustable with the size of the product being introducedinto the tank whereby the area of product passing through the tank maybe determined,

means in operative connection with the speed measuring means and theindicating means to discharge a pickling agent into the tank at a rateproportional to the area rate of passage through the tank of theproduct, and means to concurrently discharge a proportioned amount ofWater into the tank.

8. Means for continuously pickling a strip product of substantial lengthcomprising a pickling tank through which the strip product is passed ata variable speed, strip speed measuring means, means in operativeconnection therewith to introduce a pickling agent into the tank at arate proportional to the speed of passage of the strip product throughthe tank, and means to measure the rate of introduction of the picklingagent for further adjustment of the rate of introduction of saidpickling agent.

9. Means for continuously pickling a product of substantial lengthcomprising a pickling tank, product speed measuring means adjacent thepass line of the product, means responsive thereto to discharge an acidinto the pickling tank at a rate proportional to the rate of passage ofthe product through the tank, and means to introduce Water into the tankproportionally with the acid.

10. Means for continuously pickling a strip product of substantiallength comprising a pickling tank through which the strip product ispassed, means to measure and indicate the speed at which the stripproduct passes through the tank, means in connection therewith toindicate the Width of the strip product whereby the area of stripproduct passing through the tank is determined, control means inoperative connection with the speed measuring means and the indicatingmeans to discharge acid into the tank proportionally with the rate ofpassage of strip product, acid gauge means to gauge the flow of acid forfurther adjustment of the control means, second control means todischarge Water into the tank proportionally with the rate ofintroduction of acid into the tank, and water gauge means to gauge theflow of water for further adjustment of the second control means.

References Cited in the file of this patent UNITED STATES PATENTS2,334,177 Dishauzi Nov. 16, 1943 2,348,232 Trautman May 9, 19442,628,924 Johnston Feb. 17, 1953 2,661,009 Dunnegan Dec. 1, 19532,769,735 Miller Nov. 6, 1956

